Since then, Mr Morcombe and his wife Denise have been tirelessly warning Australians of the risk of child abduction and assault.

"I think it's very well recognised that children naturally are very trusting. And that's just human nature," he told Today.

"Obviously in Daniel's loss, he was a pretty smart kid but he made a mistake. He got into a car with somebody he didn't know. So he was tricked."

Sterling Free (wearing black) walks from the Kmart store, followed by a seven-year-old girl (blurred in yellow). (9News)Sterling Free walks from the Kmart store, followed by a seven-year-old girl (blurred in yellow). (9News)

Mr Morcombe said parents and carers should consider creating a "family password".

"It could be their favourite food, the sporting team they support, or their Nanna's maiden name.

"So should they be standing at a bus stop or outside school and a vehicle and a person comes up and says 'I'm looking for my pup, can you help me?' or 'You look like someone who would enjoy a piece of cake, I've got some cake in the car'.

"If that person doesn't know that password, don't go with that person."

Mr Morcombe said children should respond to what their body is telling them.

Sterling Free is seen on CCTV walking past the girl in an aisle of the Kmart store. (9News)

"Our body naturally alerts us of potential danger," he said.

"Your heart might be fluttering, butterflies in your tummy, sweating, nervous, maybe you feel like you want to go to the toilet or you're sad.

"It's your body telling you a message so we want everyone to listen to the body clues, don't disregard them, listen to them and react."

Mr Morcombe and the organisation his family started, the Daniel Morcombe Foundation, now travel to schools around the country teaching children about the threat of predators.